TSKHINVALI, Georgia, Aug. 16 -- Nine days ago, late in the afternoon of Aug. 7, Georgian tanks, artillery and infantry began moving out of bases in Georgia and toward South Ossetia, a zone long held by separatists who are backed by Moscow.

About 800 troops from Georgia's 4th Battalion left a base in Tbilisi, the Georgian capital, that Thursday afternoon, according to Georgian Defense Minister Davit Kezerashvili. Later that day, units armed with the BM-21 Grad, a multiple rocket system whose World War II version was known as Stalin's Rain, moved out of their base in Gori, about 40 miles away.

As the Georgian units approached the contested zone from the south, Russian army forces were massed just to its north, separated from it only by the 4,000-yard-long Roki Tunnel through the Caucasus Mountains. The Russian units were receiving intelligence reports about the Georgian movement. About 8 p.m., Russian military aircraft took off and skirted Georgian airspace, staying just outside it, according to Kezerashvili.

For days, separatists and Georgian troops had skirmished along the border, but this movement of armor was a major new development.

Georgia and Russia were on a collision course. In three hours, full-scale war would begin.

With a huge air, land and sea campaign, Russian forces routed the Georgians in the following days and advanced far into Georgian territory, overrunning major cities and military bases. An ensuing uproar in the West, accusing Russia of using excessive force, has clouded details of how the war began.

Interviews with Georgian leaders, Russian officials, Western diplomats and Bush administration officials, together with briefings by the Russian military in Moscow, show that a series of escalating military moves by each side convinced the other that war was imminent.

The Georgian leadership took steps, sometimes against the advice of its allies, sometimes without telling them, that accelerated the advance to a war in which Georgia could never prevail, according to a U.S. account. But the key question -- who finally triggered full conflict? -- remains in dispute. The Georgians said they staged their offensive only after Russian troops began streaming into South Ossetia and the Russians saying they advanced only after the Georgians began attacking South Ossetia's capital, Tskhinvali.

The Kremlin, long angry over Georgia's close ties with the United States and Western Europe, may have been itching for a fight, as Georgian President Mikheil Saakashvili has long insisted. If so, Saakashvili facilitated the lopsided matchup. Some Western officials say that although he faced clear provocations, he was reckless. "If it was a trap, and there's good reason to think it was, he walked right into it," one Western diplomat said, speaking on the condition of anonymity.

In Georgia, popular anger against Russia remains high, and Saakashvili has yet to be called to account for the decision to assault Tskhinvali, a small city in which thousands of civilians were forced into their cellars by shelling.

Russian officials say 2,000 people died in Tskhinvali. That figure has been described as inflated by human rights groups. But there unquestionably was a large toll of civilian deaths and injuries, which has outraged Russia and shocked Georgia's Western allies.

"It's deplorable, simply deplorable, to fire on civilians like that, and illegal," said Matthew Bryza, the U.S. special envoy to the region, in an interview. "It's horrible."